Recent theoretical findings suggest that the local flexibility of a
polymer, linked to the chemical details of the molecule, can affect both
the position and the size of knots along the polymer itself. Being of
relevance in biology and material science, we further investigate this
issue by performing molecular dynamics simulations on a model of diblock
flexible stiff polymer ring hosting a trefoil knot. We show that when
both blocks are sufficiently long to accommodate the knot, by raising
the temperature T, one may shift the knot position from the flexible
part to the stiffer one. Even a very short flexible region has a high
probability of lying within the knotted portion at lower temperatures.
In addition, we observe that there is a tendency for either extremities
of the knot to pin at the interface of the two blocks. This correlation
between knot position and bending inhomogeneity supports the view that
enzymes, binding the DNA in proximity of single-stranded gaps and nicks,
have a better chance to alter the global topology of the chain. Finally,
we observe that knots, initially squeezed within flexible portions
shorter than the typical knot size, may give rise to long-lived
metastable states.